Sorting conveyor systems are commonly found in manufacturing and storage facilities. These conveyor systems function to transport and direct articles to specific locations for later processing and/or handling. They are particularly useful, for example, in loading dock areas of manufacturing plants for directing boxed products to the desired processing or loading site.
One type of sorting conveyor system used for this purpose is commonly known as a slat sorter. This design includes a plurality of transverse tubes or slats that form the transport surface. A plurality of pusher elements or divert shoes are supported by the transport surface and are guided to travel along either of opposing sides of the surface during normal forward operation. When it is necessary to direct an article from the main conveyor run to an adjacent takeaway conveyor, a switch mechanism causes an assigned set of divert shoes to be diverted to slide across the conveyor surface in a diagonal direction. The divert shoes thus engage and direct the article to the takeaway conveyor.
In order to increase the operating efficiency of this type of conveyor, it is necessary to increase the speed with which slat sorters operate. The forward velocity of the slat sorter is limited by, among other things, the speed of the switch mechanism in selectively diverting the divert shoes. Most prior art switch actuators are pneumatically operated. When the switch actuator is activated, the switch is driven from a home position to a divert position. Upon deactivation of the switch actuator, the switch is returned to the home position by return pneumatic action or the biasing action of a return spring. The operating speed of such a switch design is limited by the physical nature of the components.
It is apparent that the lead time for signaling the activation of the switch actuator is a critical factor in proper operation. Some prior art slat sorter designs have experienced difficulty in coordinating the timing of the signal to actuate and control the switch mechanism. In fact, at faster operating speeds it may even become necessary to adjust the upstream position of the sensor that signals actuation in order to provide the proper timing. It can be appreciated that such designs require constant adjustment and, hence, are inconvenient to utilize. Further, such adjustment reduces the overall operational efficiency of these conveyor systems.
The operational speed of slat sorters is also affected by the means used to drive the transport surface. Most slat sorters with sprocket/chain assemblies use bushed chains that have moderate frictional resistance. This tends to put additional load on the prime mover. This in turn tends to inhibit conveyor speed. Other designs use a bushed chain with outboard precision bearing which adds to the complexity of the machine.
Many slat sorters are also designed with the capability of diverting packages to takeaway conveyors positioned on either side of the main conveyor. These sorters have the ability to support and guide divert shoes on either side of the transport surface and divert the shoes to shift diagonally across the surface in either direction. To achieve this end these slat sorters are provided with a divert shoe guiding network with tracks that have a crossing configuration. These designs necessarily incorporate a crossover switch at the intersection of the crossing tracks. Most prior art designs again incorporate pneumatic switches that significantly increase the complexity and thus cost of the slat sorter.
Accordingly, there is a need to overcome the drawbacks and disadvantages of the prior art designs described above. An improved divert switch is desired that will allow more efficient and dependable higher speed operation. An improved crossover switch is also needed. Both switches used in the slat sorter should be easy and economical to manufacture and offer enhanced durability for a longer service life.